Directional power dividers



July 7, 1959 A. K. WING, JR., ET AL DIRECTIONAL POWER DIVIDERS 2 Sheets-Sheet 1 Filed NOV. 20, 1953 .0 0 0 0 rco 0.0 1 00000000%000000000000000040 l Y 0 0 0 0, 0 0 0 0 0 0 w 00000000000000000 0 #0000000 .040( l .000 0 0 0 0000044410000 0 00000000000000000000000 0 0 0 0 00000000000000000000000? .0 0.000w0n0n0w0w0w030 a .0 0 l 000000000000? 0000000000n0u0n0n0u0n0u000 00000000000000004 0000. 0 v 0.000 0 0 0 01 Il.: 10Q.

| v l l l y l l 4 1 S NHS! l l l ATTORNEY July 7, 1959 A. K. WING, JR., ET AL' 2,894,168

DIRECTIONAL POWER DIVIDERS Filed Nov. 20,1955 2 Sheets-Sheet 2 4 mw Nmv .Mm .Ww QM, u

Y Y iiiiiiiiiiiii ATTORNEY United States Patent C),`

DIRECTIONAL POWER DIVIDERS Arthur K. Wing, Jr., and John H. Bryant, Nutley, NJ.,

assignors to International Telephoneand Telegraph Corporation, Nutley, NJ., a corporation of Maryland Application November zo, `195s, serial No. 393,404 s claims. (ci. als-3.6)

This invention` relates to radio frequency directional power dividers and more particularly to coupled helical radio frequency transmission lines employed `as broadband directional power dividers. p

Wave guide type Apower dividers including rectangular waveguidesand coaxial lines are well known in the art as means for providing calibrated pickupprobes, directional couplers, bifurcated` lines, and branched lines useful in monitoring transmitted radio frequency energy,-

mixing signals and so forth employing the normal radio frequency plumbing` in the UHF and microwave frequency ranges. While these devices are satisfactory for their intended uses in these frequency ranges-they tend to be `physically large `and limited to some extent in bandwidth, capabilities,

electrondischarge device field, since it is desirable to be able to handle microwaveenergies which are inherently broader inrbandwidth than the bandwidth handling capabilitiesof the usual waveguide type power dividersi,` y

1 It :well known that -helical radio frequency transmission lines, as employed in traveling wave electron discharge devices for the propagating structure therein, have a low phase velocity as compared to waveguide type radio `frequency transmission lines. 'Ihis inherent low phasevelocity means that for a given electrical length,"

helical radio frequency transmission lines for employment as `broadband directional power dividers.

Still another object of this invention is the provision of a main wave propagating structure and a secondwave propagating structure in coaxial, coupled relation to said main propagating structure, both of said structures being enclosed within an envelope` to form a traveling wave device having directional power dividing properties.

. A feature of this invention is the provision of a coupler structure coaxial of the main Wave propagatingstructure of the type employed in a traveling wave electron discharge device enabling the monitoring of the energy flowing in said mainpropagatingstructure. A l

Another -feature of this invention is the provision of la mainwave propagating structure, a coupler device coaxial o f said `propagating structure and positioning means associated with said coupler device `to position said coupler axially. with respect to said propagating structure enabling the achievement of` an energy wave phase shift.

"Still another feature of this invention is the provision This latter disadvantage` becomes ratherimportant to those working in the traveling Awave` t 52,894,168 `Patented July 7, 1959 of a phase shifting device including a main wave propagating structure having a helical coniguration and a coupler helix coaxial of said propagating structure wherein the helical coniiguration of. said coupler is a continu ation of the center conductor of a coaxial line disposed on the axis of said propagating structure and means to position said coupler helix longitudinallyl with respect to said wave propagating structure to achievea phase shift in the energy coupled from said wave propagating structure.

Further features of this invention include the provision of a coupler helix associated with each extremity and the central position of the wave propagating structure of a traveling Wave electron discharge device. The coupler helices at the extremities are `employed to couple radio frequency energy into and out `of the wave propagating structure respectively, while the `coupler helix in the central position thereof, due to its directional properties, is utilized to suppress reflected ywaves on said propagating structure.

The above-mentioned andothernfeatures and objects oi."

this invention will becomev more apparent by reference to the following description `taken in `conjunction with the accompanying drawings, in which:

Fig. l is a longitudinal sectional view of a traveling wave electron discharge device illustrating an embodiment following the principles ofthis invention;

Fig. 2 is a cross-sectional view taken along line 2-2 ofFigl; t Y

Fig. 3 is a longitudinal sectional view of a traveling wave electron discharge device illustrating another embodiment in accordancerwith thisginvention; Y

Fig. 4 is a crossfsectional view taken along line 4-4 of Fig.3; u

p Fig. 5` is a longitudinal sectional view of a phase shifting `device in laccordancewith this invention; and

. Fig. 6 is a crossfsection'al view taken` along line 6--6 of Fig. 5.

Referring to Figs. 1 .and 2, there isillustrated a traveling wave'electron discharge device comprising essentially an outer non-magneticvmetallic.. conductive envelope or shell 1 surrounding a helical type` Wavepropagating structure 2. At one end of envelopejl isA located a Vsuitable electron gun 3 for` furnishing aj concentrated stream of electrons -which pass axially through.. the interior of helical conductor 2 for collection `at a collector electrode 4 disposed atthe opposite end of envelope 1.` The electron gun 3 and collector lmayy take `any ofthe known contigurations having electrical properties suitable for this application. The various electrode potentials and means for applying them have receivedl extensivetreatment in the prior art and as-a result are omitted in the drawings of this application to simplify thegures `thereof to more clearly illustrate `the structural detailsfor` achieving the desired directional power dividersin accordance with the principles `of this invention.` y t The traveling wave electron discharge device1 is shown tohaveassociated therewith `a means 5 for producing a magnetic field whose lines of ux are parallel to the longitudinal axis of the `tube for focusingand confining the electron beam parallel to the axis ofthe tube to enhance the interaction between the electronstream and broadband radio frequency energy ,conducted along the helical path-of conductor 2. Means 5 may -be a solenoid so configured that the` desired magnetic iield is developed or it may 'comprise a permanent magnet type electron-optical device forjdevelopment-of `thedesire'd axial magnetic held. t n e 'v- Wave .propagating structure' 2 is illustrated as being supported by dielectric rods6 appropriately positioned about the circumference vvthereof to maintain structure.` 2` in a rigid, non-movable condition. Structure 2 is further illustrated as having' an'input'terminal 7 disposed adjacent theelectron"1gun"3' foi-""launchin'g'broadband radio free quency energy onto the wave propagating structure 2. As the radio frequency energy is conducted along helix minalS disposedadjacentsaid cllector4`: -Input terminal 7 andV output terminal 8v aretprovidedL with glass-beadsJ 9y and 10, respectively; to assure'tafvacuum tight envelope 2;.

As isknown, the characteristic impedance'of ahelicalpropagating structure, such=a`s 'structurel is of the order of severalhundred ohms' while radiofrequency transmis sion linesof the coaxial' type may Ibeof the order of 50 ohms, therefore, it is necessary to provide matching sections` at both the inputandioutput vportions'of the traveling wave' discharge 'device "capabl`eVof'l matching the vr50 ohm-` transmission 'lines 7 and l8i to the input and' output respectively of'the'helic'a'l' propagating structure 2.- Such a'4 matching structure is describediiriV detail in thecopending'gapplication, Seriali Number 346,086, led 'April l', 1953 in the nameaof I.' H. 'Br-yantfentitled "RadioFrequencyaMatching" Devices,` 'now U.S.V Patent' No.- 2,803,777; The lmatchingstructurendisclosedf therein includes a conductingV surface 11 included as a; portion of the envelope in close proximity f to thehelically wound structureZa, anv extension'of theY main propagating structure'z. The detailed description 'of this arrangement is covered in the above-mentioned depending application, but it is well"v to point out'here thattheclose proximity of 'conducting ysurface I1 *and #helix 2a ylprovide an impedance of approximately V50 ohms, for coupling to the 50 'ohm' radio frequency transmission line 7. 'The'impendance transfer between the 50 ohm impedance level and the several hundred'ohm impedance level of the main propagating lstructure is provided by gradually in creasing the diameter vofthe conductingcylinder; as ill1`1`strated at 12. The'ou'tput' matching' section is substantially identical to the input section just described and provides the desiredimpedancematch between the radio frequency transmission linesand vthe helical propagating structure as fully described in theabove-'identiiedjcopending application. Y f

f In accordance with thel principles ofdthis invention, a coupler helix 13 is provided in acoaxiallrelat-ion 'with wave propagating" structureV 2 having `energy input and output means as indicatedl'at 14`and 15.* By-proper' a quantityof radiofrequencypower is fed linto terminal 7 of propagatingstructure 2v and `Aassumetllat terminals 14, 15, and 8 are terminated injmatched loads. Due to the' "coupling" relationship existing' between propagating structure 2v and'couplingk `l'1elix"13,"aportionof this vradiofrequency power will appearat terminal of thecouplerA helix 'with 'the remainderjofthe power, neglecting losses in' the' propagating"structurefappearingat terminal 8 of i' propagating structurel'. lDue totheelectromagnetic field interaction between' thepropagating structureand couplin'helix 13, no power willfappear at terminal 14 of thev coupler helix.' The4 converseistatement may also be made;

namely, power fed'intolterminal: 8 of themain helicalv propagating structure Z-*would'I appear-at terminals 7 and 14With no power appearing at terminal 15.

In Ythe embodiment of Figiil and theremaining figures, cognizance must'betaken :ofi the pitch direction, thatk is,

the'v direction of,` relative," winding'pf main and coupler' helices. For some applications, the direction will be the same for both helices andfor other applications the-two helices should have opposite pitch directions, depending on factors which include primarily the degree of coupling. The proper choice of the pitch direction to use for each helix for a given application may be arrived at any one qualified in microwave circuits and electromagnetic theory. Holwever, it should be kept in mind that the degree of interactionfor coupling between the ltwo helices dependupon the 'ratioI vof radii and the phaseff. velocities kof `the two helices. -To Vgain insightintothe tions, however, f where one may wish' to couple' `power-1 gradually and will'use-fthe same'pitch-fdirection for both--4 helices: For example, it might occur'thatwithfoppositeI pitch 1 directionY the axial distance Vforcpractically complete wouldy become objectionableL- TheY embodiment illustrated in- Fig. 1v incorporatedfiir an -active traveling wave discharge device-'illustrates afpower monitor therefor." For this application; thei'couf pling between the mainI propagating structure 2` andi-title coupler helix 13 is relatively weak, `with one .'percent or lessof power on helix Zappearing at terminal 15'of tiiolf coupler helix 13 so that' the'l main helix is undisturbed for-iall `practical purposes and `enables thelobservationfbyi' means Aof metering the power handling capabilities' of"A the propagating structure 2. It maybe Well-to state'lat` thisf time that this powermonitoringA arrangement of thefvoltage .divider kof this inventionv is not 'limited `to active traveling "wave device but may be incorporated' wherever there is need to measure the power handled by a' passive helical structure' capable of being in acoaxial" arrangement with a couplinghelix substantially/fasde#y scribed herein;

Figs. 3 and 4 illustrate a travelin'gfwave devices-againVu illustrated to 'be a traveling wave electron discharge, device employing as circuit elements therein, comriail'y coupled helices following the principles of thisnventionf and performing in a novel manner certain desired' fune-f tions heretofore' achieved `by complicated,*arrangements--A for power transfer and reduction of troublesomerefl'ectedi wave energy along'the'propagating structure. Y

The traveling wave device of Figs. 3 and 4 essentiallyL4 r comprise an outer envelope 16 including therein an electron `gun V17 for production of an electron beam fori propagation along the axis of envelope 16'to a collector-1 assembly 18 at the opposite end of envelope 16. Inter-vg mediatefelectron gun 17 and collector 18 is disposed-'an interaction region 19 including a helically wound wave propagating structure 20 appropriately supported' by di electric rods 21 disposed to be maintained in rigid` relationship by aid of annular baiiies 22 and 23.`

As is common in all traveling wave electron discharge?, devices, rit is desired to couple-at the electronzgun end'i of the interaction region y19, a radio frequency *wave* forj passage along structurez whereby the desired"-inter'-' action with the electron beam emitted from electron gun 17 is achieved to realize the desired amplificationpriorf to extraction of the energy `from structure20 'at the col-- lector end thereof.-v vHeretofore, it has been the 'practice-` to incorporate complicatedf and delicate 'impedance' matching structures necessitating the proper'conii'guration of various elements closelyassociated to the'ends of theu propagating structure 20. In 'accordance 'with` theprin'ff' ciples of'fthis invention, there' is provided 'a coaxialar-" rangement of coupling helix'24 at the electron gun end 1v of propagating structure 20 `for couplingradio' frequency structure for removal of energy therefrom, said input and output means eachincludingy a helical wound conductor disposedwithin said, housingcoaxially of the appropriate extremity of saidpropagating structure and in predetermined coupled relation therewith.

3,. vIn a traveling wave electron discharge device havinga housing, an electron gun disposed in the forward end of saidhousing for projecting a beam of electrons alongy a given path toward the rearward end thereof, and a-helical wave propagating structure disposed within saidghousng eoaxially of said given path for interaction between the wave energy and the electrons of said beam, input means disposed within said housing at the forward end of said propagating structure for launching wave energy into said propagating structure, output means disposed Within said housing in the rearward end of said propaga-ting structure for removal of the interacted wave energy from said propagating structure, vand directional coupling means disposed Within said housing coaxially of said propagating structure intermediate said input and Youtput means for removal of energy from the eld of Ythe wave energy ,traveling on said propagating structure,

said input/and cmtput means each including a helical coil disposed coaxially of said forward end and said rearward end, respectively, of said propagating structure andu in predetermined coupled relation therewith.

References Cited in the le of this patent UNITED STATES PATENTS OTHER REFERENCES Text, Technique of Microwave Measurements, by Montgomery-Radiation Laboratory Series, December 20 17947, pages 873-879, para. 14.5 `and Fig. 14.24 

